Experimental Study on the Transfer of Polychlorinated Biphenyls (PCBs) and Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) into Milk of High-Yielding Cows during Negative and Positive Energy Balance

Dioxin-like polychlorinated biphenyls (dl-PCBs) as well as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are a major concern for food safety, especially in fat-containing foods of animal origin, such as milk. Due to the lipophilic character of PCDD/Fs and PCBs, it is of special interest to explore whether the metabolic state of high-yielding cows influences the transfer rates into milk. Five German Holstein cows were orally exposed to a mixture of 17 PCDD/Fs, 12 dl-PCBs, and 6 non-dioxin-like PCBs (ndl-PCBs) for two dosing periods of 28 days each. The first period covered the negative energy balance (NEB) after calving, while the second period addressed the positive energy balance (PEB) in late lactation. Each dosing period was followed by a depuration period of around 100 days. During the NEB phase, the transfer rates of 14 PCDD/Fs and 7 dl-PCBs quantified were significantly (p ≤ 0.1) higher compared to the PEB phase, indicating an influence of the metabolic state on the transfer. Furthermore, the congener-specific transfer rates (0.3–39%) were in the range of the results from former studies. This indicates that the milk yield of the exposed cows is not the only determining factor for the transfer of these congeners into milk.


S4
Sampling scheme Figure S1.Scheme of dosing periods and sampling.Cells marked as (x) indicate samples that were not taken from all experimental cows.Milk for residue analysis were sampled less frequently in the control group.

PCDD/F and PCB content in milk fat
Figure S2.Milk (left) and milk fat (right) yield of control cow 3419.

Figure S29 .
Figure S29.Distribution of fecal crude fat in samples of all cows except 3441 and 3434 during the NEB phase.Numbers in columns indicate the quantity of observations.

Table S1 .
Individual dosage of PCDD/Fs and PCBs during the first experimental phase.

Table S2 .
Individual dosage of PCDD/Fs and PCBs during the second experimental phase.

Table S4 .
Fecal crude fat values during the NEB dosing phase.

Table S5 .
Mean PCDD/F and PCB content in milk fat of the control group between day 1 and 56 postpartum during the NEB phase.was included into the experiment after the NEB phase.** Cow 3434 was excluded from mean background calculation due to health issues.

Table S6 .
Mean PCDD/F and PCB content in milk fat of the control group between day 179 and 234 postpartum during the PEB phase.

Table S7 .
Mean PCDD/F and PCB content in milk fat of the experimental group between day 22 and 29 postpartum during the NEB phase.

Table S8 .
Mean PCDD/F and PCB content in milk fat of the experimental group over the last week of the PEB dosing phase (around 200-207 days p.p.).

Table S9 .
Mean PCDD/F transfer rates derived from the milk fat content during the last week of each dosing phase.

Table S10 .
Mean PCB transfer rates derived from the milk fat content during the last week of each dosing phase.PCDD/F-and PCB-profiles for experimental cow 3438 at the end of each exposure phase (NEB and PEB).PCDD/F-and PCB-profiles for experimental cow 3448 at the end of each exposure phase (NEB and PEB).